续之二，IDesign C#编码规范之三。

34. 避免使用new继承修饰符，而是使用override。
Avoid using the new inheritance qualifier. Use override instead.
35. 对非密封类总是将public和protected方法标记为virtual。
Always mark public and protected methods as virtual in a non sealed class.
36. 除非涉及到互操作，永远不要用不安全的代码。
Never use unsafe code unless when using interop.
37. 避免显式类型转换。使用as算法防护性地转换类型。
Avoid explicit casting. Use the as operator to defensively cast to a type.
Dog dog = new GermanShepherd();
GermanShepherd shepherd = dog as GermanShepherd;
if(shepherd != null)
{...}
38. 类成员有委托时：
With delegates as class members:
a) 使用前将委托复制到局部变量，以避免并发冲突。
Copy a delegate to a local variable before publishing to avoid concurrency race condition.
b) 调用前始终检查委托是否为空。
Always check a delegate for null before invoking it.
public class MySource
{
public event EventHandler MyEvent;
public void FireEvent()
{
EventHandler temp = MyEvent;
if(temp != null)
{
temp(this,EventArgs.Empty);
}
}
}
39. 不要提供public的事件成员变量，而是使用事件访问器。
Do not provide public event member variables. Use event accessors instead.
public class MySource
{
MyDelegate m_SomeEvent;
public event MyDelegate SomeEvent
{
add
{
m_SomeEvent += value;
}
remove
{
m_SomeEvent -= value;
}
}
}
40. 使用Programming .NET Components中定义的EventsHelper类安全地发布事件。
Use the EventsHelper class defined in Programming .NET Components to publish events defensively.
41. 总是使用接口。
Always use interfaces.
a) 参见Programming .NET Components第一和第三章。
See Chapters 1 and 3 in Programming .NET Components.
42. 类和接口中方法和属性的比例至少是2：1。
Classes and interfaces should have at least 2:1 ratio of methods to properties.
43. 避免使用一个成员的接口。
Avoid interfaces with one member.
44. 努力使每个接口拥有3-5个成员。
Strive to have 3-5 members per interface.
45. 每个接口不用超过20个成员。
No more than 20 members per interface.
a) 12可能是实际应用的极限了。
12 is probably a practical limit.
46. 避免将事件作为接口成员。
Avoid events as interface members.
47. 避免使用抽象方法，而是使用接口代替。
Avoid abstract methods, use interfaces instead.
48. 在类层次中暴露接口。
Expose interfaces on class hierarchies.
a) 参见Programming .NET Components第三章。
See Chapter 3 in Programming .NET Components.
49. 优先使用明确的接口实现。
Prefer using explicit interface implementation.
a) 参见Programming .NET Components第三章。
See Chapter 3 in Programming .NET Components.
50. 永远不要假设一种类型支持某个接口。防护性地检查是否支持该接口。
Never assume a type supports an interface. Defensively query for that interface.
SomeType obj1;
IMyInterface obj2;

/* Some code to initialize obj1, then: */
obj2 = obj1 as IMyInterface;
if(obj2 != null)
{
obj2.Method1();
}
else
{
//Handle error in expected interface
}
51. 将呈现给用户的字符串永远不用硬编码，而是使用资源。
Never hardcode strings that will be presented to end users. Use resources instead.
52. 发布时可能修改的字符串永远不用